Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PORTABLE LIQUID CRYSTAL TESTING DEVICE
BACKGROUND OF THE INVENTION
This invention relatPs to an apparatus and
method for non-destructively inspecting various bodies
for discontinuities, such as flaws or internal features
such as organs in the human body.
It is known that ultrasonics can be utilized for
detecting flaws using conventional pulse echo techniques.
As a result, portable thickness meters, flaw detectors,
etc., are now availableO Some of these devices employ
extensive and expensive electronic circuitry to scan a
body and build up an electronic image. However, these
- devices do not enable the user to readily and economical-
ly visualize the flaw as a picture.
Furthermore, there has recently been developed
and disclosed a technique for inspectiny bodies which
are immersed in a liquid medium, by passing ultrasonic
energy through the object to be examined and receiving
that energy on a liquid crystal display.
~ Cdn. Palent Application, Serial No. 395/046J filed
January 27, 1982 discloses such a device. That device
includes an improved liquid crystal cell for receiving
and displaying the ultrasonic energy.
Disclosures concerning ultrasonic techniques in
general include Gooberman's text entitled Ultrasonlcs
Theory and Application, published by E.U.P~ Limited 11
"Miscellaneous Applications on Vltrasonics", subsection
1.2 "Flaw Detection". Disclosures relating to liquid
crystals may be found in the publication by E. Merck of
Darmstadt, Germanyr entitled Licristal -- ~iquid Crys-
tals; and in texts by de Genness~ Physics of Liquid
Crystals, Ox~ord Universi~y Press, 1974, and S. Chandra-
sekar, li~_ ~ , Cambridye University Press,
1978. Reference is also made to "Acousto-Hydrodynamics
Efects In Liquid Crystals" authored by J. S. Sandhu7
-- 2 --
W. G. B. Britton and R. W. B. Stephens, Physics Depart-
ment, Chelsea College, London, United Kingdom. Finally,
there are several patents which deal with related ultra-
sonic technology. See for example, Dreyer, U.S. 3,597,954,
Kessler, U.S. 3,707,323; ~, U~S. 3~831~434; and
Brenden, U.S. 3,879,989.
However, none of these references solve the prob-
lem of inspecting a large body, which cannot be immersed
in a liquid bath, for internal flaws or features, and
10 for providing a visual picture of those flaws or fea-
tures.
It is therefore the object of this invention to
provide a portable device which permits inspection of
large bodies for internal flaws or features without im-
15 mersing the body in a liquid bath and which provides a
visual image of the flaw.
Furthermore~ one of the problems in the medical
field has been to provide a suitable non-invasive diag-
nostic technique for internal human examination. Pre-
20 sently ultrasonics is used for internal human examina-
tion, but the apparatus which is used is large, includes
extensive costly electronics, and is not portable. Thus
the patient must be brought to the ultrasonic testing
device rather than the device being carried by a physi-
2S cian to the patient. Moreover, the electronics is re-
quired to provide a visual image of the area being exam-
ined due to the present state of the technology.
It is therefore an object of this invention to
provide a portable ultrasonic device which permits inter-
30 nal human e~samination and which can be carried by a
physician to the patient.
These and other objects of the invention will
become apparent from the following speciEication and ap-
pended claims.
SUM~RY OF TEIE INVENTION
There is provided by this invention a portable
flaw detecting device which employs a liquid crystal
display cell. The device includes an ultrasonic trans-
ducer and liquid crystal display cell which receivesreflected or scattered ultrasonic energy and displays
the flaws or features which are detected.
More particularly, the device includes a first
housing having a transducer support member for support-
ing the transducer in relation to the surface of theobject to be examined. A second housing is provided
and includes a liquid crystal display support for posi-
tioning and supporting the liquid crystal cell in rela
tion to the surface. Interconnecting means are provided
for interconnecting the two housing members in adjustable
and angular relation ~o each other. The angular relation~
ship generally is selected so as to receive reflected or
scattered energy from the body.
The liquid crystal support member is a generally
elongated hollow tubular member having a viewing end and
a surface contact end. The liquid crystal display cell
is positioned intermediate the ends. The surface con-
tacting end is provided with an acoustical coupler (e.g.,
acoustical matching layers) which permits the reflected
or scattered energy to be efficiently received by the
liquid crystal cell. A liquid coupling medium is posi-
tioned between the coupler and the liquid crystal cell,
and, if necessary, a variable focal length acoustic lens
is also provided. Appropriate illumination is also pro-
vided in the system.
It has been found that using this system permitsinspection of large bodies, which cannot be readily im-
mersed, for flaws and features, as well as for inspect-
ing the human body. It is anticipated that this device
will find a number of uses for physiological examination.
3%
As described hereinafter, these devices include
a liquid crystal cell having a particular laminated
construction and the coupling medium is important depend-
ing upon the material or body to be examined.
BRIEF DESCRIPTION OF THE DRAWINGS
. . _ _
FIGURE 1 is a sectional view showing a portable
display device of a type suitable for use in connec-tion
with inspecting for internal flaws on large bodies;
FIGURE 2 iS a sectional view showing the construc-
tion of a liquid crystal display cell;
FIGURE 3 is a sectional view showing a laminatedstructure for transmitting acoustic energy; and
FIGURE 4 is a sectional view showing a device for
use in examining human bodies.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, there is shown a port-
able testing device 10 generally, which is shown resting
on the surface of a large, rigid body 12, which has an
interior flaw 14.
The device 10 includes three main assemblies,
which are the transducer housing 16, liquid crystal
housing 18, and the interconnecting member 20.
The transducer housing 16 supports therein a stan-
dard ultrasonic transducer 22 which is powered by the
supply 24. In addition to standard transducers, trans-
ducer arrays which can provide beam steering can be used.
~he housing 16 orients the transducer so that the trans-
ducer's radiation axis is at an angle with respect to
the surface 12.
The liquid crystal display housing 18 includes a
viewing end 18a and a contact end 18~.
~5~
A multi~layer liquid crystal display cell 26 is
Eixedly secured in the tubularly-shaped support housing
18 intermediate the ends 18a and 18b.
The contacting end 18b includes an acoustic
S coupling member 28 which is adapted to contact the sur~
face 12 and acoustically couple thereto so as to mini-
mize acoustic losses between the surface 12 and housing
18.
The device as shown includes a variable focal
length acoustic lens 30 which is positioned b~twe~n the
coupler 28 and the liquid crystal display 26. The cou-
pler, lens and display are acoustically coupled to each
other through a liquid medium which fills the space be-
tween (1) the coupler and lens and (2) the lens and dis-
play.
The display 26 is viewed from the viewing end 18a.A reflected light system is shown for enhancing the image
on the display. However, as described hereinafter, a
transmitted light system may also be used. The reflected
light system includes an objective lens 32, a polarizer
34, a half~silvered mirror 36, a polarizer 38, and a
light source 40.
A concave reflecting mirror arrangement 42 and a
black, light-absorbiny surface 43 are provided on oppo-
site sides of the housing 18.
Details of the liquid crystal cell 26 and couplingmember 28 will be described hereinafter.
The interconnecting means 20 is provided for ad-
justably interconnecting and fixing the relative posi~
tioning of the transducer housing relative to the liquid
crystal housing 18. It could generally be stated that
the interconnecting means can be used to assure the rela-
tive positioning of the transducer and liquid crystal
cell in a reflection-receiving relationship.
The interconnecting member 20 includes an upper
slide 20a and a lower slide 20b. Intermediate the slides
is a thumb screw adjuster 20c which includes a pair of
3~:
oppositely threaded members that can be operated by a
thumb screw to controllably move the housings 16 and 18
together and apart. In this embodiment the housing mem
bers are moved linearly with respect to each otherO
In operation the transducer ~2 emits ultrasonic
energy which passes through body 12 and strikes the flaw
14. The energy striking the flaw 14 is reflected or
scattered in many directions, but some energy is directed
toward the liquid crystal cell 26. That energy passes to
the coupling member 28 and into the transmitting medium
in contact therewith. The lens 30 is then used to foc~s
the energy onto the liquid crystal cell 26.
An image is then formed by the interaction of
the ultrasonic energy and the liquid crystal molecules
in the cell.
The image on the cell is viewed by illuminating
the surface of the cell via the lamp 40 and half-silvered
or semi-reflecting mirror 32. The image can thus be seen
by the viewer 41, through the lens 32, through polarizer
34, and through the half-silvered mirror 36.
Referring now to the liquid crystal display 26,
the display includes, as shown in Figure 2, two covers
44 and 45, each of which are acoustically transparent,
rigid and at least one of which is optically transparent.
A liquid crystal material ~8 is positioned between the
covers 44 and 45 and sealed in place by the use of a
peripheral spacer 50.
The preferred liquid crystal material used in the
cell herein is of the nematic type which is homeotropi-
cally aligned (i.e., the molecules are on average normalto the cover surfaces).
It is also desirable that the cell be as trans-
parent to the sonic energy as ~ossible. In other words
sonic energy striking the surface of the cover 45 and
transmitted through the entire cell should be maximized
and absorption and internal reflection minimized, since
9~2
they will degrade the image quality. It is also desir-
able that the acoustic properties of the cell be ~ery
similar to the properties of the surrounding medium,
which in this case is water on one side and air cn the
other side. However, the cell should also be useful with
water/water interfaces.
It has been determined .hat if the thickness of
the cover is much much less than one-fourth of the wave-
length of the sound wave propagating through the cover
(i.e., WL/4), then thickness effects relating to the
sonic absorption could be ignored for analytical purposes
at normal incidence (i.e., the ultrasonic beam is per-
pendicular to the cover). For the optically transparent
cover 45, glass has been used although other transparent
materials may be used.
It has been found that glass slides or panes which
are available in thickness of 200 micrometers or less are
sufficient to avoid any considerations concerning absorp-
tion or reflection. However, such thin slides are very
flexible and would not assure proper alignment of the
li~uid crystal molecules in uniform thickness of a liquid
crystal layers.
It has been found that in order to provide the
desired rigidity, the glass cover must be of a laminated
structure having at least two glass panes.
In Figure 3 a five-layer thick glass cover is
shown. There are provided three glass la~ers 52, 54, and
56 and two intermediate adhesive layers 58 and 60. It is
desirable that each of the layers be of a thickness much
much less -than WL/4 for the appropriate material so that
for absorption purposes the individual thicknesses can
be ignored. The ~uestion then is: What is the acoustic
impedance of the composite structure? A calculation
based on the empirically determined formula:
1 = 1 = 1 = 1 = 1 = 1
ZC Zg Za Zg Za Zg
can be used. ZC is the impedance of composite, Zg is the
impedance of glass, and Za is the impedance of the adhe-
sive which is estimated to be similar to the impedance of
Plexiglas or Lucite.
Laminated structures described above can be suc-
cessfully employed in cell 26 for both covers.
In addition, the acoustic coupling member 28 can
be provided of a similar laminated structure which assures
proper acoustic matching between the surface of the body
to be examined and the acoustic medium whlch is carrying
the signal to the display cell.
Referring now to Figure 4, another embodiment 100
of the portable tester is shown. The tester lO0 is sim-
ilar to the tester shown in Figure l, except that it in-
cludes a transmissive optical system rather than reflec-
tive, but it should be appreciated that transmissive or
reflective systems are similar and either can be selected
based upon factors such as end use r ease of operation,
etc.
Furthermore, the tester 100 is shown resting on
a soft surface 102, such as a human body, and is useful
in examining internal organs or for tumors and the like.
Referring now to Figure 4, there is shown a trans-
ducer housing 104, and a liquid crystal dlsplay housing
106, each of which are similar to the corresponding parts
in Figure l, as well as interconnecting means108. The
interconnecting means 108 provides a pivoting motion so
as to permit adjustment to soft surfaces. The intercon-
necting means includes a pivot point 108a, such as a hinge,
that connects the two housings at their lower ends and
a thumb wheel assembly 108b that also pivotally connects
the housings and by a pair of oppositely threaded members
that permits the housings to be drawn together or sepa-
rated. Of course depending upon the end use, the pivot-
ing interconnection and the linear interconnection can beused interchangeably.
~ ~ ~15~ ~3 ~
g
The principal difference relates to the optical
system 110 generally, which is o the transmissive type.
In this system, there is provided an acoustic reflector
112 which directs acoustic energy to the display cell
114 in the side of the housing. The specific construc-
tion for the reflector is disclosed in patent applica-
tion, Serial No. 395~046. The acoustic reflector is op-
tically transparent and light from the source 116
passes through the acoustic reflector 112, illuminates
and passes through the liquid crystal display cell.
Appropriate polarizers and reflectors are provided so that
the image on the cell can be seen by the viewer 118.
This type of device can be ~sed or physiological
examination. For example, a tumor, such as 120, can be
located and viewed using this device, in the same manner
as internal flaws can be located. Internal organs can
also be located.
It will be appreciated that numerous changes and
modifications can be made to the devices disclosed here-
in without departing from the spirit and scope of thisinvention.
